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a wire, b, at their upper ends.

UNTTEE STATES PATENT OEEicE.

,THOMAS A. EDISON, OF MENLO PARK, NEW JERSEY, ASSIGNOR TO THE EDISONELECTRIC LIGHT COMPANY, OF NEW YORK, N. Y.

INCANDESCENT ELECTRIC LAMP.

QPIERCIFICATION forming part of Letters Patent No. 317,633, dated May12, 1885.

Application filed November 9, 1882. (No model.)

.40 all whom it may concern.-

Be it known that I, THOMAS A. EDISON, of Menlo Park, in the countyof'Middlesex and State of New Jersey, have invented a new and usefulImprovement in Incandescent Electric Lamps, (Case No. 507,) of which thefollowing is a specification. 7

In my application No. 506 (Serial No. 76,378) I have set forth variousmeans by which the flexible carbon filament of an incandescing electriclamp may be removably attached to the leading-in wires. The object I nowhave in view is to provide, in connection with such removable connctions, means for compensating for the expansion and contraction causedby the heating and cooling of the filament, so as to prevent any bendingor breaking of such filament. I prefer to accomplish this by attachingto the filament a spiral spring whose tension is in the same directionas the expansion and contraction of the filament, and such spring beingalso firmly attached to the glass of the lamp-globe, so that when thefilament expands the spring will contract, and when the filamentcontracts the spring will lengthen.

My invention is illustrated in the annexed drawing, in which the figureis an elevation of a lamp embodying the invention.

The incandescing conductor consists of two straight filaments of carbon,aa, connected by To the other end of each is attached ahook, c. The endsof the leadingin wires 1 2 are i'ormedinto corresponding hooks, dd. Thefilament is inclosed in the glass vacuum-chamber A, at whose top is theprojection 13, of sufficient diameter to allow the incandescingconductor to pass through it when the glass is cut or otherwise removedfrom the top of said projection.

A glass tube,f, is sealed in the top of the globe, and a platinum wire,g, is sealedin said tube. The wireg terminates in a spring, h, which isattached to the wire 12. Such spring serves to keep the hooks in goodelectrical and mechanical contact, to keep the carbon upright, and tocompensate for the expansion and contraction of the carbon.

What I claim is- 1. In an incandescing electriclamp, the combination,with the carbon filament, of removable connections with the leading-inwiresand a tension-spring drawing upon such filament, to compensate forthe expansion and contraction of the filament. substantially as setforth.

2. In an incandescing electric lamp, the combination, with the straightcarbon filaments connected by a wire, of the tension-spring attached tosaid wire and sealed in the glass of the in -.losing-globe,substantially as set forth.

3. In an incandescing electrielamp, the combination, with the straightcarbon filaments connected by a wire, of the tensionspring attached tosaid wire and sealed in the glass of the inclosingglobe, and removableconnections between said filaments and the leading in wires,substantially as set forth.

This specification signed and witnessed this 26th day of October, 1882.

THOS. A. EDISON.

l/Vitnessesz WM. H. MEADOWCROFT, H. W. SEELY.

